It is generally known, as for example indicated in U.S. Pat. No. 4,732,879, that fibrous glass substrates such as, for example, woven fabrics, can be employed as filter bags for numerous and a wide variety of applications. One of the outstanding benefits of employing a fibrous glass substrate in the filter bag fabric is that glass has a high temperature resistance. Consequently, it is possible to employ such bags in high temperature atmospheres.
One of the problems, however, in employing a fibrous glass substrate as the fabric for a filter bag is the need for such glass fibers to be abrasion resistant and also to have a long flex-life. Glass is quite susceptible to abrasion and scratching of the glass leads to inferior strength In order to prevent scratching fibers not only need to be resistant to the abrasion of particulates that are being separated by filtration, but also must possess self-abrasion resistance.
As is known in the art, filter bags need to be cleaned and this cleaning typically takes one of two forms. In one, the bags are mechanically shaken such as for example by violent vibration. In another, the bags are cleaned by periodically pulsing them with blasts of air. It will thus be seen, that the bags are consequently subjected to violent flexing. There is therefore a need for the fibers to also have a long flex-life.
TEFLON material has been used as a coating for fibers used in a filter bag. While this material does provide increased abrasion resistance, it is not generally suitable for long term, high temperature applications, e.g. operation at temperature on the order of about 350.degree. C. Neither is such a material generally suitable as a support, or undercoat, for catalytically active materials.
In accordance with the present invention a method is provided which satisfies this need in the art and which solves the existing problem. That is, a method is provided for forming an abrasion resistant, long flex-life coating on a fibrous glass substrate. In a preferred embodiment of this invention this abrasion resistant, long flex-life coating can then be overcoated with catalytically active materials such as disclosed in incorporated U.S. Pat. No. 4,732,879 and used as a catalytically active filter bag.